Modify API for SimpleHttpClient.get_json and update usages.

Previously, this would only return the HTTP body as JSON, and discard other
response information (e.g. the HTTP response code). This has now been changed
to throw a CodeMessageException on a non-2xx response, with the response code
and body, which can then be parsed as JSON.

Affected modules include:
 - Registration/Login (when using an email for IS auth)

synapse/http/client.py

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
+from synapse.api.errors import CodeMessageException
 from synapse.http.agent_name import AGENT_NAME
 from twisted.internet import defer, reactor
 from twisted.web.client import (
@@ -83,7 +83,7 @@ class SimpleHttpClient(object):
 
     @defer.inlineCallbacks
     def get_json(self, uri, args={}):
-        """ Get's some json from the given host and path
+        """ Gets some json from the given host and path
 
         Args:
             uri (str): The URI to request, not including query parameters
@@ -91,15 +91,11 @@ class SimpleHttpClient(object):
                 None.
                 **Note**: The value of each key is assumed to be an iterable
                 and *not* a string.
-
         Returns:
-            Deferred: Succeeds when we get *any* HTTP response.
-
-            The result of the deferred is a tuple of `(code, response)`,
-            where `response` is a dict representing the decoded JSON body.
+            Deferred: Succeeds when we get *any* 2xx HTTP response.
+        Raises:
+            On a non-2xx HTTP response.
         """
-
-        yield
         if len(args):
             query_bytes = urllib.urlencode(args, True)
             uri = "%s?%s" % (uri, query_bytes)
@@ -114,7 +110,10 @@ class SimpleHttpClient(object):
 
         body = yield readBody(response)
 
-        defer.returnValue(json.loads(body))
+        if 200 <= response.code < 300:
+            defer.returnValue(json.loads(body))
+        else:
+            raise CodeMessageException(response.code, body)
 
 
 class CaptchaServerHttpClient(SimpleHttpClient):